Hand powered vehicles are well represented in the prior art; however, a large percentage of the designs have major flaws which might well prevent their commercial success.
Among the most prevalent of these flaws is the lack of simplicity, which make the cost of these items, most of which might be classified as children's toys, prohibitive. The extra components also require extra energy to operator, especially the reciprocating components, and they add to the weight and upkeep. For instance, U.S. Pat. No. 5,272,928, to Young, U.S. Pat. No. 5,690,346, to Keskitalo, and U.S. Pat. No. 6,554,309, to Thir, all use at least four one-way clutches with associated chains, sprockets, drums, etc. In U.S. Pat. No. 6,557,879, Caldwell uses ten pages of drawings to illustrated his design, and Keskitalo, in U.S. Pat. No. 5,690,346, requires seven pages of drawings. In U.S. Pat. No. 5,050,864, Pertramer discloses a very complicated drive mechanism for a scooter, as does Chait, in U.S. Pat. No. 6,708,997.
Several of the designs appear to have a small enough movement per stroke that a fast stroke cycle is necessary to maintain a reasonable speed. This, in turn, causes an inefficient operation, as the power losses in reversing the reciprocating components increase as the square of the velocity.
For those designs which utilize a spring to rewind one or more one-way clutches on the reverse stroke, the spring is almost always a problem. Providing the necessary distance capacity and strength for the spring is always a challenge, and in several of the designs in the prior art the spring design appears to be inadequate. Patents in this group include U.S. Pat. No. 5,690,346 to Keskitalo, and U.S. Pat. No. 5,272,928 to Young. In contrast, Chait, in his U.S. Pat. No. 6,942,234, shows us return springs which appear adequate, but which will consume a noticeable amount of power.
The steering mechanism is questionable in U.S. Pat. No. 6,942,234, to Chait, which involves tilting the propulsion levers, and U.S. Pat. No. 5,690,346, to Keskitalo, and U.S. Pat. No. 5,272,928, to Young, both utilize a very small pulley on the steering column which is activated by cables, and very likely does not operate properly. It would appear that the design in U.S. Pat. No. 4,109,927, to Harper, would not permit turning of the hand driven crank while in a turning mode.
U.S. Pat. No. 5,282,640, to Lindsey, discloses a scooter that is propelled by back-and-forth reciprocation of a single handlebar. It is doubtful that this will be effective, as the operator is not able to spread his feet front-to-back on the platform in order to exert enough horizontal force on the handlebars. This is in contrast to the present invention, which uses vertical force to operate the mechanism, and the operator can easily apply his weight to the handlebars.
U.S. Pat. No. 2,123,390, to Welch, and U.S. Pat. No. 1,598,855, to Dunlop, operate in a manner similar to the Lindsey design, and would probably present the same problem.
Designs in this field probably have a greater chance of success if they are uncomplicated and have a small number of lightweight reciprocating components.